Automatically-operated sliding doors of varying types are well known and in widespread commercial use. Typically, the operation of such doors is electromechanically controlled by actuation from a weight-sensitive mat, a photoelectric eye, or similar devices for sensing the approach or presence of a person or object at the door requiring its opening.
Such automatic sliding doors are typically installed where a need exists to accommodate high volumes of traffic, e.g., supermarkets, retail stores, banks, airports, hospitals, etc. However, even in such uses, traffic volume ordinarily varies widely over time. As will be recognized, when traffic volume is low, say where opening actuation occurs only once every 20-30 seconds or less often, only one person typically is passing through the door during each opening actuation. Under such circumstances, the doors need not open fully as under high traffic conditions when a number of persons may pass through the doors together or in succession. However, all conventional automatic sliding doors have actuating and control arrangements which are incapable of opening the doors to differing widths under differing traffic conditions, but instead are set to always open whenever actuated to the fullest extent necessary under heavy traffic conditions, regardless of the actual traffic volume.
It will be appreciated that each opening actuation of such doors results in the loss of heated or cooled air. Thus, the conventional set-up of such doors to open fully even under low traffic conditions causes significantly greater such losses over time than would occur if the doors were opened each time only to the extent necessary in relation to the prevailing traffic conditions.